Burner control system



United States Patent 3,228,448 BURNER CONTROL SYSTEM M. R. Jayaram, Long Beach, Calif., assignor to Honeywell Inc, lVlinneapolis, Minn, a corporation of Delaware Filed May 6, 1965, Ser. No. 456,037 Claims. (Cl. 158-28) This application is a continuation-in-part of copending application Serial Number 396,651, now abandoned, which was filed on September 15, 1964, in that the present application discloses an additional FIGURE 4. The above mentioned copending application is a division and a continuation-in-part of a prior filed copending application Serial Number 288,275, now Patent 3,196,923, which was filed on June 17, 1963.

This application contains claims generic to all four figures.

This invention is concerned with an improved burner control system and particularly with such a system having a minimum number of components and being constructed and arranged to provide direct ignition of a main burner by the use of line voltage components.

The burner control system of my invention utilizes a unique circuit construction by which an ignition means, in the form of an ignition transformer, and a fuel controller, in the form of a fuel valve, are connected in circuit branches to be controlled by circuits which share common electrical components. The energization of the control system is controlled by a controller switch which is adapted to close upon the need for operation of an associated fuel burner unit, and is also controlled by a normally closed switch of a safety cutout means having a bimetal and a heater which form a time delayed switch actuator.

A further portion of the unique circuit includes flame switch means which is connected in circuit with the ignition transformer and fuel valve.

Detection of flame is effective to operatively deenergize the ignition transformer upon the presence of flame. In a modification of my invention the ignition transformer is de-energized by the flame detector through the expedient of an ignition timer.

Terminals of the unique circuit are connected to the heater of the safety cutout means to operatively energize this heater, as controlled by the flame switch means. After a time period of heater energization, indicative of a failure to establish or maintain flame, cutout occurs and circuit means are provided to maintain the safety cutout means in this cutout condition by maintaining its heater energized.

My invention will be apparent to those skilled in the art upon reference to the following specification, claims and drawings, of which:

FIGURES 1, 2, 3 and 4 are schematic representations of three embodiments of my invention.

Referring to FIGURE 1, reference numeral 10 designates a controller in the form of a thermostat bimetal switch which is responsive to the temperature of an area to be heated by an associated fuel burner, not shown. Upon the temperature of this area dropping, indicating a need for operation of the fuel burner, controller 10 closes its switch.

Closing of controller 19 is effective, as Will be apparent, to energize a fuel valve 11 and an ignition transformer 12. Fuel valve 11 is connected in a fuel conduit, not shown, and is a normally closed fuel valve which is effec tive when operatively energized to allow fuel to flow to the fuel burner where it is then ignited by means of ignition electrodes 13 connected to the secondary winding of ignition transformer 12.

A flame detector is shown in schematic form as having a closed switch 14 which is adapted to open on the "Ice presence of flame at the burner. An operator 15 is adapted to open switch 14 of the flame detector and this operator may be controlled electrically, as by a relay responsive to a photocell viewing the flame, or may be operated by a bimetal actuator, or similar actuator responsive to the presence of flame at the burner. It suffices to say that switch 14 opens on the presence of flame.

Reference numeral 16 identifies safety cutout means having a bimetal 17, a heater 18 associated with bimetal 17 to form an actuator, a closed switch 19 and an open switch 20. Energization of heater 18 for a given time period is effective to cause bimetal 17 to move in the direction of the arrow labelled H to open switch 19 and close switch 20.

The burner control system of FIGURE 1 utilizes an arrangement in the form of a bridge circuit. This bridge circuit can be seen to have a first leg including a resistor 21, a second leg including the primary winding 22 of ignition transformer 12, a third leg including a resistor 23, and a fourth leg including fuel valve 11. The terminals identified by reference numerals 24 and 25 can be considered to be input terminals of the bridge circuit, whereas the terminals identified by reference numerals 26 and 27 can be considered to be the output terminals of this bridge circuit.

As can be seen, resistor 21 is shorted by flame detector switch 14 when this switch is in a position indicating the absence of flame. Also, the output terminals, that is terminals 26 and 27 of the bridge circuit, are connected to opposite terminals of heater 18 of safety cutout means 16.

The input terminals 24 and 25 of the bridge circuit are connected to a pair of power line conductors 30 and 31 by means of a series circuit which includes the switch of controller 10 and the closed switch 19 of safety cutout means 16.

Considering the operation of my improved burner control system, a call for operation of an associated fuel burner unit is evidenced by closing of controller 10. A circuit can now be traced from conductor 31 through controller 10, conductor 32, bimetal 17 and switch 19 of safety cutout means 16, input terminals 25 and 24 of the bridge circuit, and conductor 33 to the other power line conductor 30.

Fuel valve 11 is energized to pull in by way of a circuit which can be traced from bridge input terminal 25 through fuel valve 11, bridge output terminal 27, conductors 34 and 35, safety cutout means heater 18, conductor 36, bridge output terminal 26, conductor 37, closed flame detector switch 14, and conductor 38 to power line conductor 30.

The primary winding 22 of ignition transformer 12 is operatively energized, to produce sparking at electrodes 13, by way of a circuit which can be traced from bridge input terminal 25 through primary Winding 22, bridge output terminal 26, conductor 37, flame detector switch 14, and conductor 38 to power line conductor 30.

It should also be noted that circuits can be traced from bridge input terminal 25 to power line conductor 30 by way of fuel valve 11 and resistor 23, and by way of primary winding 22 and resistor 21. However, the impedance magnitude of the resistors 23 and 21, respectively, are such that while limited electrical energization is applied to both the fuel valve and the ignition transformer through these circuits, the fuel valve and the ignition transformer are not operatively energized by way of these circuits. Operative energization of transformer 12, and pull in of valve 11 requires that flame detector switch 14 be closed to establish the first above traced circuits.

More particularly, the impedance value of resistor 23, connected in circuit with fuel valve 11, is such as to maintain the fuel valve operatively energized, or pulled in,

once it is initially pulled in by means of the first above traced circuit. The impedance value of resistor 21 is such that opening of fiame detector switch 14 operatively deenergizes ignition transformer 12 to interrupt the sparking at electrodes 13 thereof.

Referring again to the initial energizing circuit of fuel valve 11, this initial energizing circuit includes in series therewith heater 18 of safety cutout means 16 to operatively energize this heater. Since fuel is supplied to the burner and ignition transformer 12 is energized, flame is normally established at the burner within a short time period, shorter than the timing period of safety cutout means 16. Flame detector switch 14 then opens. The opening of this switch places resistor 21 in series with primary winding 22 of ignition transformer 12, and as above mentioned, operatively de-energizes this ignition transformer. Also, the opening of flame detector switch 14 now causes fuel valve 11 to be maintained operatively energized through a circuit which can be traced from the bridge input terminal 25 through the fuel valve, bridge output terminal 27, resistor 23, bridge input terminal 24, and conductor 33 to power line conductor 30. As has been mentioned, this circuit supplies sufficient electrical energy to the fuel valve to maintain the fuel valve energized, but not of a magnitude to initially operatively energize the fuel valve.

Heater 18 of safety cutout means 16 is connected across the output terminals 26 and 27 of the bridge circuit formed of the components 21, 22, 23 and 11. Once flame is detected, the bridge circuit is substantially balanced and heater 18 is operatively de-energized. This is the running condition of my improved burner control system.

If a flame failure is subsequently experienced, flame detector switch 14 closes and the above described initial conditions are re-established whereby ignition transformer 12 is again energized and the bridge is unbalanced to the extent that safety cutout means heater 18 is now energized.

If flame is not subsequently re-established, safety cutout means 16 is eflective, after a time period of energization of heater 18, to open switch 19 and close switch 20.

The opening of switch 19 disconnects the bridge input terminal 25 from the source of voltage 30-31.

The closing of switch 20 completes a series circuit which now connects the bridge output terminals 26 and 27 to power line conductors 30 and 31. Since heater 18 is connected directly to these output terminals 26 and 27, heater 18 is likewise connected to the power line conductors 30 and 31. This can be seen by tracing a circuit from power line conductor 31 through controller 10, conductor 32, bimetal 17 and switch 20 of safety cutout means 16, a resistor 40, a conductors 34, bridge output terminal 27, bridge output terminal 26, conductor 37, flame detector switch 14, and conductor 38 to power line conductor 30. Since heater 18 is directly connected to the bridge output terminals 26 and 27, heater 18 is maintained energized by way of this above traced circuit, resistor 40 functioning as a current limiting resistor. Thus safety cutout means 16 is maintained in an actuated or cutout condition, with switch 19 open and switch 241 closed. To reset safety cutout means 16 to the starting condition, it is necessary that controller be manually opened for a time period suficient to allow bimetal 17 to cool and again close switch 19 and open switch 20. The apparatus is then in a condition to again attempt to establish flame at the fuel burner. Thus, it is possible to reset safety cutout means 16 froma remote position, since electrical reset is provided.

In FIGURE 2 I disclose a further embodiment of my invention wherein the bridge circuit configuration is not used, and the heater 18 of the safety cutout means 16 is directly energized and de-energized by a switch 116 of a flame detector having an operator 115. Furthermore, ignition transformer 12 has its primary winding 22 connected directly in series with a normally closed switch 114 of the flame detector.

In the disclosure of FIGURES 2, 3 and 4 structural elements which are similar to those disclosed in FIGURE I retain like reference numerals. It should be noted however that certain electrical characteristics, such as impedance values of the various electrical components, may be adjusted to accommodate the somewhat different circuit construction of FIGURES 2, 3 and 4.

In the device of FIGURE 2 fuel valve 11 is again operatively energized by means of a circuit which includes the normally closed switch 19 of safety cutout means 16 and also includes heater 18 and normally closed switch 116 of the flame detector. Once valve 11 is operatively energized, it is maintained in this condition by holding resistor 23. As with the circuit of FIGURE 1, the impedance value of resistor 23 is such as to maintain the fuel valve operatively energized. However, the fuel valve cannot be initially energized through the circuit including resistor 23.

The detection of flame by the flame detector causes the switches 114 and 116 to open to deenergize both the ignition transformer 12 and the heater 18 of safety cutout means 16. This de-energization is accomplished directly by the opening of switches in a series circuit with these electrical components.

In the event of safety cutout action, heater 18 of safety cutout means 16 is maintained continuously energized to maintain a lock out condition by means of a circuit which includes the resistor 40, heater 18, and the normally closed switch 116 of the flame detector. Here again, it is necessary to open thermostat 10 to reset safety cutout means 16.

In FIGURE 3 I disclose yet a further embodiment of my invention wherein the ignition transformer 12 and the heater 18 of safety cutout means 16 are directly controlled by means of a normally closed switch 214 of the flame detector, and wherein the flame detector includes a normally open switch 216 connected in circuit with resistor 23. The flame detector is constructed and arranged such that its operator 215 is effective to switchs 214 and 216 with overlapping action. That is, switch 216 closes before switch 214 opens.

In the construction of my invention as exemplified by FIGURE 3, fuel valve 11 is initially energized and ignition transformer 12 is energized in much the same manner described in connection wit-h FIGURE 2. The opening of switch 214 of the flame detector, in response to the presence of flame, is effective to de-energize the primary winding 22 of the ignition transformer 12 and to also de-energize heater 18 of safety cutout means 16. The detection of flame by the flame detector also causes switch 216 to close and the closing of this switch completes a holding circuit for fuel valve 11 through resistor 23. Here again, the impedance magnitude of resistor 23 is such as to prevent initial energization of fuel valve 11 through this circuit. Thus, fuel valve energization is prevented in the event of a momentary power failure in which the fuel valve 11 closes. The re-establishment of power before switch 216 opens does not energize valve 11 because of the impedance magnitude of resistor 23.

In FIGURE 4, I disclose a further embodiment of my invention wherein the ignition transformer 12 is controlled by rneans of an ignition timer 320. This ignition timer is a bimetal type timer having a heater 321 associated with a bimetal operator 322 and having normally closed switches 323 and 324. Upon heating of bimetal 322, switches 323 and 324 move to an open position. Energization of heater 321 is achieved by means of a normally open switch 316 of the flame detector.

In the construction of my invention as exemplified by FIGURE 4, fuel valve 11 is initially energized by way of a circuit which includes controller 10, normally closed switch 19 of the safety cutout, fuel valve 11, heater 18 of the safety cutout, normally closes switch 314 of the flame detector, and normally closed switch 323 of ignition timer 320. From this circuit it can be seen that the ignition timer must be in its cold position to close switch 323 before fuel valve 11 can be energized.

Ignition transformer 12 is energized by way of a circuit which can be traced through controller 19, switch 19 of the safety cutout, primary winding 22 of the ignition transformer, and the normally closed switch 324 of the ignition timer. From this circuit it can be seen that ignition transformer 12 is directly under the control of the ignition timer.

Upon flame being detected, switch 314 opens and switch 316 closes. By virtue of a shunt circuit for the fuel valve which extends through the heater 321 of ignition timer 320, it is unnecessary in the circuit construction of FIG- URE 4 that switches 314 and 316 overlap in their operation. The opening of switch 314 opens the circuit to heater 18 of the safety cutout and operatively de-energizes this heater in response to the presence of flame. The closing of switch 316 completes a holding circuit to shunt switch 323 of the ignition timer, this holding circuit being effective after the timing period of the ignition timer.

The opening of switch 314 of the flame detector is effective to operatively energize heater 321 of the ignition timer by virtue of the fact that continued energization of the fuel valve 11 is now achieved by a circuit which extends through heater 321. As with the construction of FIGURES 1, 2 and 3 the impedance value of heater 321 is of a value to maintain fuel valve 11 energized and of a high enough value to prevent initial energization of the fuel valve through this circuit. For ex ample, if a momentary power failure should occur, fuel valve 11 is de-energized and cannot be re-energized through the circuit which includes heater 321. It is necessary for the flame detector to reclose switch 314 to establish a circuit through heater 18 of the safety cutout in order to re-energize the fuel valve.

After a time period of energization of heater 321, switch 324 opens and de-energizes ignition transformer 12. The action of the ignition timer is to provide an ignition overrun, extending the ignition period beyond the detection of flame by the flame detector. Subsequent to the opening of switch 323, the control apparatus is maintained energized from power line conductor 30 through the switch 316 of the flame detector.

As with FIGURES 1, 2 and 3, safety cutout 16 includes a normally open switch 29 which, in combination with a resistor 40, provides a lockout condition for the safety cutout.

From the above description, it can be seen that I have provided a unique burner control system wherein an ignition transformer and a fuel valve are directly connected in circuit with a minimum of other electrical components to provide the optimum in simple and yet reliable direct ignition of a fuel burner. The structure of my invention provides a minimum of circuit connections to operatively control the components of a fuel burner with circuits, which share common elements, to thereby provide safe operation of the burner unit with a minimum of expense.

Modifications of my invention will be apparent to those skilled in the art and it is thus intended that my invention be limited solely by the scope of the appended claims.

I claim as my invention:

1. Burner control apparatus for use with a fuel burner unit having a valve to control the flow of fuel to a burner and having ignition means operative when energized to ignite fuel at the burner, the apparatus comprising: safety cutout means having a normally closed switch and time delayed actuator effective after a time period of energization thereof to open said switch, flame sensing means adapted to sense the presence or absence of flame at the burner and having a normally closed switch which is opened upon the presence of flame; first circuit means including said safety cutout means switch and said flame sensing means switch and adapted to energize the ignition means; second circuit means including said safety cutout means actuator, said safety cutout means switch, and said flame sensing means switch and adapted to energize both said safety cutout means actuator and the valve; impedance means; and third circuit means including said impedance means and said safety cutout means switch and adapted to maintain energization of the valve upon opening of said flame sensing means switch in response to the presence of flame at the burner, said impedance means being of a sutficiently high magnitude to prevent operative energization of the valve.

2. Burner control apparatus for use with a fuel burner installation having an electrically energizable normally closed fuel valve to control the flow of fuel to a burner, and having electrically energizable ignition means associated with the burner to directly ignite the fuel, the apparatus comprising: a flame detector having switch means adapted to be actuated upon the establishment of flame at the burner; a safety switch having an electrically energizable time delay actuator and a normally closed and a normally open switch controlled thereby; energizing circuit means forming a closed circuit to a source of electrical power and adapted to energize the fuel valve and including in series connection the switch means of said flame detector, the actuator of said safety switch, and the normally closed switch of said safety switch; holding circuit means forming a closed circuit to the source of electrical power and adapted to maintain the fuel valve energized and including in series connection an electrical impedance and the normally closed switch of said safety switch, the impedance value of said impedance being selected to prevent initial energization of the fuel valve by said holding circuit means; energizing circuit means forming a closed circuit to the source of electrical power and adapted to energize the ignition means and including in series connection the switch means of said flame detector and the normally closed switch of said safety switch; and lockout circuit means forming a closed circuit to the source of electrical power and including in series connection the switch means of said flame detector, the actuator of said safety switch, a lockout impedance element, and the normally open switch of said safety switch.

3. Burner control apparatus for use with a fuel burner installation having an electrically energizable normally closed fuel valve to control the flow of fuel to a burner, and having electrically energizahle ignition means associated with the burner to directly ignite the fuel, the apparatus comprising: a flame detector having a normally closed switch and a normally open switch which are adapted to be actuated upon the establishment of flame at the burner; a safety switch having an electrically energizable time delay actuator and a normally closed and a normally open switch controlled thereby; energizing circuit means forming a closed circuit to a source of electrical power and adapted to energize the fuel valve and including in series connection the normally closed switch of said flame detector, the actuator of said safety switch, and the normally closed switch of said safety switch; holding circuit means forming a closed circuit to the source of electrical power and adapted to maintain the fuel valve energized and including in series connection an electrical impedance, the normally open switch of said flame detector, and the normally closed switch of said safety switch; energizing circuit means forming a closed circuit to the source of electrical power and adapted to energize the ignition means and including in series connection the normally closed switch of said flame detector and the normally closed switch of said safety switch; and lockout circuit means forming a closed circuit to the source of electrical power and including in series connection the normally closed switch of said flame de- 7 tector, the actuator of said safety switch, an electrical impedance, and the normally open switch of said safety switch.

4. Burner control apparatus for use with a fuel burner installation having an electrically energizable normally closed fuel valve to control the flow of fuel to a burner, and having electrically energizable ignition means associated with the burner to directly ignite the fuel, the apparatus comprising: a flame detector having a normally closed switch and a normally open switch which are adapted to be actuate-d upon the establishment of flame at the burner; a safety switch having an electrically energizable time delay actuator and a normally closed and a normally open switch controlled thereby; an ignition timer having an electrically energizable time delay actuator and a normally closed switch means controlled thereby; energizing circuit means forming a closed circuit to a source of electrical power and adapted to energize the fuel valve and including in series connection the normally closed switch means of said ignition timer, the normally closed switch of said flame detector, the actuator of said safety switch, and the normally closed switch of said safety switch; holding circuit means forming a closed circuit to the source of electrical power and adapted to maintain the fuel valve energized and including in series connection the actuator of said ignition timer, the normally open switch of said flame detector, and the normally closed switch of said safety switch; energizing circuit means forming a closed circuit to the source of electrical power and adapted to energize the ignition means and including in series connection the normally closed switch means of said ignition timer and the normally closed switch of said safety switch; and lockout circuit means forming a closed circuit to the source of electrical power and including in series connection the normally closed switch of said flame detector, the actuator of said safety switch, an electrical impedance, and the normally open switch of said safety switch.

5. Burner control apparatus for use with a fuel burner unit having a valve to control the flow of fuel to a burner and having ignition means to directly ignite fuel at the burner, the apparatus comprising; a bimetal type ignition timer having a heater and a normally closed switch means; circuit means adapted to connect said ignition timer heater in circuit with the valve, said heater being of sufficient magnitude to prevent operative energization of the valve when in series therewith but being sufficiently small in magnitude to permit the valve to remain operatively energized after having been initially operatively energized; normally closed bimetal type safety cutout switch means having a heater; and normally closed combustion responsive switch means adapted to open upon combustion being sensed; a starting circuit adapted to be connected to the valve and including said safety cutout means heater,

said combustion responsive switch means, said safety cutout switch means, and said ignition timer switch means, said starting circuit being independent of said ignition timer heater and operatively energizing said safety cutout means heater and the valve; a holding circuit for the valve including said ignition timer heater so that when said combustion responsive switch means opens the valve remains operatively energized through said holding circuit; a holding circuit for said safety cutout means heater including said combustion responsive switch means and independent of the valve so that in the absence of combustion said safety cutout means heater is maintained energized while the valve is de-energized and the safety cutout switch means is held in an open position.

6. Burner control apparatus for use with a fuel buner unit having a valve to control the flow of fuel to a burner and having ignition means to ignite fuel at the burner, the apparatus comprising: safety cutout means having a normally closed switch, a normally open switch, and time delayed actuating means effective after a time period of energization thereof to actuate said switches; flame sensing means adapted to sense the presence or absence of flame at the burner; first circuit means including said normally closed safety cutout means switch and means controlled by said flame sensing means adapted to energize the ignition means; second circuit means including said safety cutout means actuator, said normally closed safety cutout means switch, and means controlled by said flame sensing means adapted to energize both said safety cutout means actuator and the valve; impedance means; third circuit means including said impedance means and said normally closed safety cutout means switch and adapted to maintain energization of the valve upon said flame sensing means sensing the presence of flame at the burner, said impedance means being of a suflrciently high magnitude to prevent operative energization of the valve by Way of said third circuit means, and fourth circuit means including said normally open safety cutout means switch, means controlled by said flame sensing means, and said safety cutout means actuator to maintain energization of said safety cutout means actuator while the valve is deenergized in response to the absence of flame at the burner.

7. Burner control apparatus for use with a fuel burner unit having a valve to control the flow of fuel to a burner and having ignition means to directly ignite fuel at the burner, the apparatus comprising; a bimetal type ignition timer having a heater and a first and second normally closed switch; bimetal type safety cutout means having a normally closed switch, a normally open switch and a heater; combustion responsive means having a normally closed switch and a normally open switch; an ignition circuit adapted to be connected to said ignition means and including said normally closed safety cutout switch and said first ignition timer switch; a starting circuit adapted to be connected to the valve and including said safety cutout heater, said normally closed combustion responsive switch, said normally closed safety cutout switch, and said second ignition timer switch, said starting circuit being independent of said ignition timer heater and operatively energizing said safety cutout heater and the valve; a holding circuit for the valve including said ignition timer heater and said normally open combustion responsive switch so that when said normally closed combustion responsive switch opens the valve remains operatively energized through said holding circuit; said ignition timer heater being of sufl'icient magnitude to prevent operative energization of the valve when in series therewith but being sufliciently small in magnitude to permit the valve to remain operatively energized after having been initially operatively energized; and a holding circuit for said safety cutout heater including said normally closed combustion responsive switch and said normally open safety cutout switch and independent of the valve so that in the absence of combustion said safety cutout heater is maintained energized while the valve is de-energized and the normally open safety cutout switch is held in an open position.

8. Burner control apparatus for use with a fuel burner installation having an electrically energizable normally closed fuel valve to control the flow of fuel to a burner, and having electrically energizable ignition means associ ated with the burner to directly ignite the fuel, the apparatus comprising: a flame detector having a normally closed switch which is adapted to be opened upon the establishment of flame at the burner; a safety switch having an electrically energizable time delay actuator and a normally closed and a normally open switch controlled thereby; energizing circuit means forming a closed circuit to a source of electrical power and adapted to energize the fuel valve and including in series connection the normally closed switch of said flame detector, the actuator of said safety switch, and the normally closed switch of said safety switch; holding circuit means forming a closed circuit to the source of electrical power and adapted to maintain the fuel valve energized and including a first electrical impedance connected in parallel with the normally closed switch of said flame detector; energizing circuit means forming a closed circuit to the source of electrical power and adapted to energize the ignition means and including in series connection the normally closed switch of said flame detector and the normally closed switch of said safety switch; and lockout circuit means forming a closed circuit to the source of electrical power and including in series connection the normally closed switch of said flame detector, the actuator of said safety switch, a second electrical impedance, and the normally open switch of said safety switch.

9. Burner control apparatus for use with a fuel burner installation having an electrically energizable normally closed fuel valve to control the flow of fuel to a burner, and having electrically energizable ignition means associated with the burner to directly ignite the fuel, the apparatus comprising: a flame detector having a first and a second normally closed switch which are adapted to be opened upon the establishment of flame at the burner; a safety switch having an electrically energizable time delay actuator and a normally closed and a normally open switch controlled thereby; energizing circuit means forming a closed circuit to a source of electrical power and adapted to energize the fuel valve and including in series connection said first normally closed switch of said flame detector, the actuator of said safety switch, and the normally closed switch of said safety switch; holding circuit means forming a closed circuit to the source of electrical power and adapted to maintain the fuel valve energized and including in series connection a first electrical impedance and the normally closed switch of said safety switch; energizing circuit means forming a closed circuit to the source of electrical power and adapted to energize the ignition means and including in series connection said second normally closed switch of said flame detector and the normally closed switch of said safety switch; and lockout circuit means forming a closed circuit to the source of electrical power and including in series connection said first normally closed switch of said flame detector, the actuator of said safety switch, a second electrical impedance, and the normally open switch of said safety switch.

10. In a burner control system; a normally closed electrically energizable fuel valve; a resistor connected in circuit with said valve, said resistor being of suflicient magnitude to prevent the operative energization of said valve when in series therewith but being sufficiently small in magnitude to permit said valve to remain operatively energized after having been initially operatively energized; safety cutout means comprising a time delayed actuator and a closed switch controlled by said actuator and movable from a closed position to an open position after a time period of energization of said actuator; combustion responsive means including a switch which is closed when said combustion responsive means is not sensing combustion; a starting circuit for said valve including said safety cutout means actuator, said combustion responsive means switch, and said safety cutout means switch, said starting circuit being independent of said resistor and operatively energizing said safety cutout means actuator and said valve; a holding circuit for said valve including said resistor and said safety cutout means switch so that when said combustion responsive means switch opens said valve remains operatively energized through said holding circuit; a holding circuit for said safety cutout means actuator including said combustion responsive means switch and independent of said valve so that in the absence of combustion said safety cutout means actuator is maintained energized while said valve is de-energized so that said safety cutout means actuator holds said safety cutout means switch in said open position in which said valve remains de-energized; and a controller connected between a source of power and each of said starting and holding circuits; said safety cutout means being operative automatically to return said safety cutout means switch to said closed position upon de-energization of said safety cutout means actuator as a result of operation of said controller to permit re-establishment of said starting circuit.

References Cited by the Examiner UNITED STATES PATENTS 2,544,511 3/1951 Pratt 15828 2,842,192 7/ 1958 Penn 15828 3,059,693 10/ 1962 Hotchkiss 158125 3,079,984 3/1963 Wright et a1 158125 JAMES W. WESTHAVER, Primary Examiner. 

1. BURNER CONTROL APPARATUS FOR USE WITH A FUEL BURNER UNIT HAVING A VALVE TO CONTROL THE FLOW OF FUEL TO A BURNER AND HAVING IGNITION MEANS OPERATIVE WHEN ENERGIZED TO IGNITE FUEL AT THE BURNER, THE APPARATUS COMPRISING: SAFETY CUTOUT MEANS HAVING A NORMALLY CLOSED SWITCH AND TIME DELAYED ACTUATOR EFFECTIVE AFTER A TIME PERIOD OF ENERGIZATION THEREOF TO OPEN SAID SWITCH, FLAME SENSING MEANS ADAPTED TO SENSE THE PRESENCE OR ABSENCE OF FLAME AT THE BURNER AND HAVING A NORMALLY CLOSED SWITCH WHICH IS OPENED UPON THE PRESENCE OF FLAME; FIRST CIRCUIT MEANS INCLUDING SAID SAFETY CUTOUT MEANS SWITCH AND SAID FLAME SENSING MEANS SWITCH AND ADAPTED TO ENERGIZE THE IGNITION MEANS; SECOND CIRCUIT MEANS INCLUDING 